Speaking at the Japan Press Club in Tokyo Tuesday, Junichiro Koizumi, who served as prime minister from 2001 to 2006 and led the Liberal Democratic Party of Japan, said, "I think we should go to zero nuclear power now."
All 50 of Japan's working reactors remain offline, pending safety checks after the March 2011 Fukushima nuclear power plant disaster triggered by a massive earthquake and tsunami.
Shinzo Abe, the current prime minister and LDP leader, wants to have Japan's reactors brought back online after the country's nuclear regulatory agency declares them safe. He's also in favor of selling Japan's nuclear technology to other countries.
"Restarting the reactors will only result in the buildup of more nuclear waste materials," Koizumi said.
Koizumi had, for the most part, remained out of the spotlight since leaving office, and Tuesday's press conference was his first since retiring from politics in 2008.
Lately, however, the former prime minister has spoken out against nuclear power. A poll published Tuesday in the Asahi Shimbun newspaper indicated 54 percent of those surveyed favor his anti-nuclear stance.
Opposition parties are mostly opposed to nuclear power, Koizumi said, and about half of the ruling LDP lawmakers are as well. If Abe were to pursue a nuclear-free society, "many pro-nuclear LDP lawmakers will follow his determination," he added.
Koizumi dismissed criticism that he is not suggesting specific solutions to meet Japan's energy needs.
"It is impossible for me alone to show alternative proposals. If politicians adopt a broad policy, people with wisdom will undoubtedly present good ideas," he said. "The government should think about converting to and promoting renewable energies by gathering experts, bureaucrats and other intellectuals."
Koizumi was a staunch supporter of nuclear power as prime minister, but has attributed his about-face to a visit to an underground repository for spent nuclear fuel in Finland in August, where he learned those radioactive materials would have to be sealed off for 100,000 years.
"Is it really possible to continue to store [nuclear waste] for such a long period?" he asked Tuesday, noting Japan is an earthquake-prone country and its bedrock is not strong.
But Abe's top spokesman, Yoshihide Suga, on Tuesday downplayed the government's focus on nuclear power, maintaining that providing a stable supply of energy was the top priority.
"The government is responsible for ensuring a constant and stable supply of energy," China's Xinhua News Agency reported Suga told a press briefing. "We need to make sure that energy supply remains inexpensive and in this regard, there is no change to our policy of keeping nuclear power to a minimum," he said.